1. Field of the Invention
This invention relates to antennas and more particularly to a phase scan antenna array for planar radar scanning in a single plane with a substantially pencil-shaped beam.
2. Description of the Prior Art
Radar system antennas are usually designed to be scanned in two, orthogonally-related planes, such as azimuth and elevation, for example. For some applications, however, the antenna need only be scanned in a single plane because other means are available to provide scanning in the orthogonally-related plane. For example, if such an antenna capable of scanning only in a single plane is mounted in a moving vehicle, such as an aircraft, a terminally-guided weapon or a remotely-piloted vehicle, for example, and if the motion or track of the vehicle is along a path which is orthogonally-related to the scanning plane of the antenna, then scanning is effectively provided in two, orthogonally-related planes.
Since such single planes scanning antennas are often mounted in the moving vehicle itself, the size and weight of the antenna and its associated scanning system become very important. For example, when such antennas are used in aircraft, terminally-guided weapons and remotely-piloted vehicles, it is essential that the antenna and its scanning system be as compact as possible and of extremely small size and low weight. Accordingly, antenna systems which are mechanically scanned or driven are usually not feasible for applications of this type because of the complexity and size and weight of the scanning system.
Although electronically "steered" phased array systems have been developed which do not rely upon mechanical scanning or drive mechanisms, they usually require very complex and bulky scanning control arrangements because a large number of phase shifting circuits are required for the individual antenna elements making up the array. Furthermore, the phase scan array systems are expensive to manufacture. Additionally, for some applications, it is desirable that the antenna array be both conformal and frangible. For example, in certain types of terminally-guided weapons, the antenna array must be so mounted in the body of the guided weapon that it is directly in the path of a small projectile or charge which must be fired through the array before impact with the target, so that the array must be easily fractured or broken. For the same application, the limited space available in such guided weapons for mounting the antenna array makes it desirable that a conformal antenna array be employed which can be bent or deformed to some degree to facilitate mounting and placement of the array on or within the weapon.